1 General Provisions
1.0.1 This code is formulated to standardize design of vertical cylindrical welded steel oil tanks and make it advanced in technology, cost-effective, safe and applicable and high quality.
1.0.2 This code is applicable to design of vertical cylindrical welded steel oil tanks at and close to normal pressure for storing petroleum and petrochemical and other similar liquid but it is not applicable to design of buried tank, tank holding extremely and highly hazardous medium and artificial refrigerant fluid tank.
1.0.3 Design of vertical cylindrical welded steel oil tanks shall comply with not only this code but the current relevant national standards.
2 Terms
2.0.1 Annular/sketch bottom plates
The outermost bottom plates at the lower part of shell plates.
2.0.2 Annular bottom plates
Annular/sketch bottom plates with polygonal or circular inner edge.
2.0.3 Bottom plates
Bottom plates except edge plate.
2.0.4 Fixed roofs
Roof around which shell ends are fixed and connected, mainly including types as follows:
1 Self-supporting cone roof: with circular cone roof and supported only by the shell periphery;
2 Column-supported cone roof: with circular cone roof and supported by shell, girder, column or other structure;
3 Self-supporting dome roof: with spherical roof and supported only by the shell periphery.
2.0.5 Floating roofs
Roof which lifts with the liquid level, including external floating roof, in an open-top oil tank and internal floating roof, in fixed-roof oil tank. Generally the floating roof tank refers to external floating roof tank if not specified. There are major floating roofs as follows:
1 Single-deck floating roof: with annular seal cabin around floating roof and single deck in the middle;
2 Double-deck floating roof: entire floating roof is composed of compartments;
3 Open-top bulk-headed floating roof: with annular open-top compartments around the floating roofs and single deck in the middle and this type is only applicable to internal floating roof;
4 Floating roof on floats: plates keep clear of the liquid level, being floated by the float, only applicable to internal floating roof.
2.0.6 Design pressure
Maximum pressure set at the gas phase room on top of tank (gauge pressure, the same below) shall not be less than the maximum operating pressure likely to be present in normal use.
2.0.7 Metal temperature
Average temperature of shell plates and pressure components along section thickness.
2.0.8 Design temperature
Metal temperature of shell plates and pressure components given under the normal operation of tanks.
2.0.9 Calculated thickness
Thickness obtained by calculation according to the formulae specified in this code.
2.0.10 Design thickness
The sum of calculation thickness and corrosion allowance.
2.0.11 Nominal thickness
Design thickness with tolerance, which is rounded up to standard thickness of materials.
2.0.12 Available thickness
Nominal thickness minus additional thickness
2.0.13 Wind girder
Members arranged on the shell to make it stronger to resist wind.
2.0.14 Stiffening ring
Members arranged on the shell to enhance the stability of tank shell and protect it against instability.
2.0.15 Rolling ladder
Walkway which connects shell roof platform and floating roof and lifts with the floating roof.
2.0.16 Automatic bleeder vent
Venting device which opens/closes automatically when the floating roof rises or is restored to bracing state.
2.0.17 Primary roof drains
Equipment which drains the rainwater on external floating roof out of the tank under normal conditions.
2.0.18 Emergency roof drains
Safety devices which discharge excessive seeper on external floating roof in emergency circumstances.
2.0.19 Circulation vent
Venting device which is arranged on the internal floating roof tank shell or fixed roof in a circular manner.
3 Basic Requirement
3.0.1 For the atmospheric pressure tank at fixed roof, the negative pressure is designed to be 0.25kPa or less and the lifting force generated from positive pressure shall not exceed the total weight of roof plate and the appurtenances thereon; if as specified in Appendix A of this code, the maximum design pressure may be increased to 18kPa; if as specified in Appendix B of this code, the maximum design negative pressure may be increased to 6.9kPa. The atmospheric pressure of floating roof tank is used as the design pressure.